Microscopy is developed to the state where it can complement X-ray crystallography and multi-dimensional NMR by determining the three- dimensional localization of labeled proteins and nucleic acids in cells and subcellular proteins. Especially powerful is correlated light and electron microscopy in which labeled proteins can be found first at the subcellular or organellar level using laser scanning confocal and multi- photon microscopies and after additional specimen preparation, these labels can be visualized at high resolution with an intermediate high- voltage electron microscope (IVEM). The purpose of the Microscopy ore is to provide excellent facilities and the expertise to make it possible for all members of this program to apply state-of the-art microscopy techniques with no need for prior experience in microscopy methods. For suitable imaging studies the Microscopy Core will have access to the extensive facilities and highly knowledgeable staff of the National Center for Microscopy and Imaging Research at San Diego (NCMIR). Unique capabilities developed or improved at NCMIR include: (1) Fluorescence photo-oxidation, which has proven to be a valuable tool for studying the three-dimensional (3-D) organization of cellular constituents by confocal microscopy and intermediate high-voltage electron microscopy (2) Electron tomography, which can explore the 3 D distributions of immunolabeled components of kinase anchoring proteins and associated supramacromolecular and cellular components, (3) Multi-labeling (sometime called multi-color) immuno-confocal light microscopy to localize two or more molecular species using fluorophores with different excitation and/or emission wavelengths and (4) Several software packages which are critical for the visualization and interpretation of structural information derived from microscope images.